2×20.
Potamogeton amplifolius
×
Potamogeton praelongus
→ This rare pondweed hybrid known from
ME,
VT. It has leaf blades that are weakly arched, sessile to somewhat clasping, and with mostly 15–21 veins. The tips of the leaf blades split in pressing (as in
Potamogeton praelongus). The stems have dark blotches.

20×23.
Potamogeton praelongus
×
Potamogeton richardsonii
→ This rare pondweed hybrid is known from
CT; also reported from
MA by Angelo and Boufford (2000), but the specimen (at
MASS!) has a qualified (i.e., tentative) determination and is equivocal. It is intermediate in morphology between its parental species.